500
sin a =3/5=y/r sin b=5/13=y/r cos a=x/r=-4/5
x^2+y^2=r^2 x^2+y^2=r^2 cos b=x/r=-12/13
x^2+3^2=5^2 x^2+5^2=13^2 sin(a+b)=(sin a)(cos b)
x^2=25-9 x^2=169-25 +(cos a)(sin b)
x=±√16 x=±√144 =(3/5)(-12/13)+(-4/5(5/13)
x=-4 x=-12 =-56/65
Evaluate sin (a+b), where a and b are obtuse angles; sin a =3/5 and sin b =5/13